1. Field of the Invention
The present disclosure generally relates to wireless communications and more particularly relates to systems and methods for retransmission of multicast traffic over a secure wireless local area network (WLAN).
2. Background Information
Among other things, FIG. 1 illustrates a typical network configuration for communicating data between stations via an access point in a WLAN or 802.11-based network. As illustrated in the non-limiting example of FIG. 1, a network 140 may be coupled to access point 130. In some embodiments, the network 140 may be the Internet, for example. Access point 130 can be configured to provide wireless communications to various wireless devices or stations 110, 120, 124. Depending on the particular configuration, the stations 110, 120, 124 may be a personal computer, a laptop computer, a mobile phone, a personal digital assistant (PDA), and/or other device configured for wirelessly sending and/or receiving data. Furthermore, access point 130 may be configured to provide a variety of wireless communications services, including but not limited to: Wireless Fidelity (WIFI) services, Worldwide Interoperability for Microwave Access (WiMAX) services, and wireless session initiation protocol (SIP) services. Furthermore, the stations 110, 120, 124 may be configured for WIFI communications (including, but not limited to 802.11, 802.11b, 802.11a/b, 802.11g, and/or 802.11n).
Access point 130 can transmit to a single station such as station 110 which is known as a unicast transmission. Access point 130 can also transmit to all stations which is known as a broadcast transmission. Access point 130 can also transmit to a subset of all stations which is known as multicast transmissions. In broadcast and multicast (collectively referred to as BM), a receiver may be an endpoint where it simply receives a BM transmission or it may be responsible for relaying the transmission to the next stage (e.g. an access point).
In the past, BM transmissions in wireless networks and in particular 802.11 WIFI networks are transmitted once, without retries. The primary reason for the lack of retries in BM transmissions is that there is no mechanism by which receivers can indicate whether a BM frame was received or not.
Recently, there have been discussions and proposals that would introduce retries into BM transmissions. One difficulty arises due to the absence of retries in older system's legacy receivers (either stations or access point). There was no mechanism by which receivers can indicate whether a frame was received or not. Because a legacy receiver will be unable to determine whether a BM transmission is a retry, legacy receivers will likely assume the BM transmission is a new transmission. The legacy receiver having the belief there are no retries for BM transmissions will assume the current BM transmission is a new BM transmission resulting in the generation of duplicate frames through the media access control (MAC) service access point where higher level protocol in the network protocol stack will see duplicates, resulting in the end application on the station seeing duplicate frames, which is highly undesirable.
One prior proposed solution is to modify the destination address or the basic service set identification (BSSID) of the retried BM frame in such a way that a legacy receiver would simply ignore the BM frame as not designated for it. The approach can work in general, but in a protected environment where all data frames are encrypted, there is a serious drawback. Because fields such as the destination address and BSSID are included in the additional authentication data (AAD), a change in these fields can cause the AAD to change. The AAD is used to determine the encryption key. A change in any field in the AAD will yield a different encryption key. As a result in order for the retried BM frame to be viable, the frame body would have to be re-encrypted using the modified encryption key. The additional encryption can be costly in terms of processor resources. Accordingly, various needs exist in the industry to address the aforementioned deficiencies and inadequacies.